Vapor generators with superheat temperature control



June 4, 1957 E. e. HUTCHINGS VAPOR GENERATORS WITH SUPERHEAT TEMPERATURECONTROL 2 Shee'ts-Sheet 1 Filed Aug. 21, 1952 F G. INVENTOREdward-Gfluicizizz 5 ATTORNEY 2 Sheets-Sheet 2 E. G. HUTCHINGS VAPORGENERATORS WITH SUPERHEAT TEMPERATURE CONTROL /5:5 fi nnnnnnnnnn flfiNVENTOR Edward G fuzckz'ngs 'ATTORNEY FlG.3 2+- FIG.4' 24- June 4, 1957Filed Aug. 21, 1952 United States Patent VAPOR GENERATORS WITH SUPERHEATTEMPERATURE CONTROL Edward G. Hutehings, Whitton, Twickenham, Engiand,assignor to The Bahcoclr & Wilcox Company, New York, N. Y., acorporation of New Jersey Application August 21, 1952, Serial No.305,602

Claims priority, application Great Britain September 5, 1951 Claims.(Cl. 122-477) This invention relates to tubular vapor generating andsuperheating units of the kind comprising parallel connected gas passesleading from a combustion chamber and a vapor heater so disposed inrelation to the passes that the vapor temperature at the outlet from theheater may be controlled by regulation of the distribution of theheating gas flow between the passes. In such a unit there may be, forexample, two parallel passes generally with the whole superheaterdisposed in one of the passes,

although the superheater may be arranged with substantially the wholethereof disposed in one pass and the remainder thereof disposed in theother pass. In a marine steam boiler, for instance, normally a highsteam temperature is required, so that the dampers of the pass inparallel with the superheater pass are nearly closed. On the other hand,when maneuvering, a low steam temperature is required, so that thedampers of the superheater pas-s are nearly closed. In both cases,therefore, a resistance to gas flow is set up by the dampers. An objectof the invention is the provision of improved means for controlling thedistribution of gas flow between the parallel gas passes of a tubularvapor generating and superheating unit.

The present invention includes a tubular vapor generating andsuperheating unit comprising parallel connected gas passes leading froma combustion chamber and a vapor heater so disposed in relation to thepasses that the vapor temperature at the outlet from the heater may becontrolled by regulation of the distribution of the heating gas flowbetween the passes, together with control means arranged differentiallyto vary flow areas of gas paths respectively in series with the saidpasses and containing heat exchange means, and thereby to regulate thedistribution of gas flow between the passes while minimizing unbalanceof draft loss between said parallel passes and difference in gas outlettemperatures from the continuations of said passes over portions of saidheat exchanger.

The invention also includes a tubular vapor generating and superheatingunit comprising inclined vapor generating tube banks at opposite sidesof a combustion chamber and extending between lower lateral liquid drumsand a central upper vapor and liquid drum, the drums having their axesparallel to one another, respective tube screens between the banks andthe combustion chamber, and a superheater between one of the tubescreens and the corresponding bank, a boiler casing providing passagesadapted to lead the gases flowing from the respective tube banks torespective spaces above the front and rear parts of the vapor and liquiddrum, an economizer in a gas uptake above said spaces, bafilestransverse to the axis of the vapor and liquid drum subdividing the gasflow past economizer surfaces into separate gas passages, and a swingingdamp-er adapted selectively to determine whether a passage betweenadjacent bafiies shall receive gas from the one or from the other of thesaid spaces.

The invention will now be described, by way of ex- 2,794,427 PatentedJune 4, 1957 ice ample, with reference to the accompanying drawings, inwhich:

Fig. 1 illustrates a scheme of gas flows past heat exchange surfaces,including vapor heating surfaces, of a vapor generating and superheatingunit having control means for diflerentially varying the flow areas ofcertain heating gas paths, and

Figs. 2 to 4 show elements of a water tube marine boiler, Fig. 2 being afront elevation thereof in section on the lines 22 of Figs. 3 and 4,Fig. 3 being an outside view from the left of the upper part of theboiler, as indicated by the line 3-3 of Fig. 2, part of the casing beingshown broken away, and Fig. 4 being a side view from the left of theupper part of the boiler in section on the line 4-4 of Fig. 2.

In Fig. 1 of the drawings elements of a vapor generating andsuperheating unit are indicated; combustion gases are shown as flowingfrom a combustion chamber 1 to deliver heat to heat exchange surfacesdisposed in two gas passes 2 and 3 arranged for the flow of combustiongases in parallel therethrough and then to deliver heat to an economizer4 in a subsequent gas pass 5 connected to suitable draft producingmeans, such as an induced draft fan (not shown). The heat exchangesurfaces in the first parallel pass 2 consist of a vapor generatingscreen section 6 and, in the gas flow path behind the screen section, avapor generating section 7, and the heat exchange surfaces in the secondparallel pass 3 consist of a vapor generating screen section 8, asuperheater 9 in the gas flow path behind the screen section 8, and avapor generating section 10 in the gas flow path behind the superheater9. The gases from the first and second parallel passes 2 and 3 are ledto respective spaces 11 and 12 in front, as regards the direction of gasflow, of the economizer 4 and on opposite sides of a swinging damper 13,which can be moved to one side or other of a neutral position so as torestrict to a greater or lesser extent the gas flow into the economizer4 from either the space 11 or the space 12.

In the gas pass 5 a number of baflies 14-18 are provided which extendthrough the economizer 4, and extend parallel to opposite walls 19 and26 of the gas pass 5 and to the axis of the damper 13 and subdivide thegas pass 5 into a number of separate passages 21-26. The damper 13 andthe bafiies 14-18 are so arranged that the damper can determine by itsposition whether any of the passages 22-25, lying between the twooutermost passages 21 and 26, which latter are respectively adjacent thegas pass walls 19 and 20, is included in the gas path from the space 11or the gas path from the space 12. As shown, the edge of the damperremote from its axis is adjacent the bafiie 15, and a gas pathconsisting of the passages 21 and 22 arranged in parallel is placed inseries with the gas pass 2 containing the screen section 6 and vaporgenerating section 7, and a gas path consisting of the passages 23-25arranged in parallel is placed in series with the gas pass 3 containingthe screen section 8, superheater 9 and vapor generating section if Therelative quantities of gases flowing in the gas passes 2 and 3 dependupon the respective flow areas of the paths consisting of the passages21 and 22 and of the passages 23-26. A second damper 27, which in itsopen position lies against the wall 20 but which closes towards thedamper 13, is provided for independently varying the relative gasquantities flowing through the passes 2 and 3.

In the operation of the unit, by varying the position of the damper 13so that the gas passage previously in one gas path in the pass 5 isinstead included in the other gas path in the pass 5 and adjusting sofar as necessary the firing rate of the combustion chamber so that thesame pressure, the superheat temperature at a given load can be varied;alternatively, by appropriately varying the position of the damper 13 asthe load changes, the superheat temperature can be regulated over arange of loads. If a superheat temperature is required which is betweenthat obtained with the damper edge positioned adjacent one baffle andthat obtained'with the damper edge positioned adjacent the next bafile,then the damper may beset to that of the two positions yielding thehigher superheat temperature and the gas flow through the gas path 3including the superheater 9 is reduced by operating the second damper 27to a suitable extent from the open towards the closing position.

The arrangement provides a simple method of superheat control. It willbe observed, moreover, that the turning of the damper 13 to a positionin which it is effective to reduce the flow area in the gas pass for thegases from one of the gas passes 2 and 3 is simultaneously effective toincrease the flow area in the gas pass 5 for the gases from the other ofthe two gas passes 2 and 3; it follows that the gas flow resistance ofthe unit as a whole is not so greatly increased as otherwise, and hencethe available draft or fan power is used more effectively; and thatthose gases in the gas path of which the flow area is increased arecaused to contact more economizer surface and hence leave the unit withless heat than otherwise would be the case; in other words the boilerefliciency is increased. Dampers 13 and 27 are arranged so that they maybe brought to positions in which they together prevent the flow of gasesinthe pass 3 in which the superheater 9 is arranged. If they are broughtto such positions for the starting up of the unit, the starting up maybe hastened without the risk of damaging the superheater, which hasinitially no steam flow therethrough.

Figs. 24 are views of a water tube marine boiler having a steam andwater drum 5! extending from the front to rear above a combustionchamber 51 arranged to be fired through its front wall by oil burners52. A water drum 53 below the drum 5t and to the right of the combustionchamber 51 is connected with the drum 50 by an inwardly and upwardlyinclined bank 54 of vapor generating tubes, and a water drum 55 belowthe drum 50 and to the left of the combustion chamber 51 is connected tothe drum 50 by an inwardly and upwardly inclined bank 56 of vaporgenerating tubes. On the combustion chamber side of the bank 54 arethree rows of screening tubes 57. On the combustion chamber side of thebank 56 are three rows of screening tubes 58, and between the rows ofscreening tubes 58 and the bank 56 is a bank of superheater tubes 59.

Above the drum 50 is a gas uptake 60 in which is arranged an economizer61. The casing 62 on the righthand side of the boiler is designed so asto lead gases flowing upwardly and outwardly through the rows ofscreening tubes 57 and the bank 54 to a space 63 above the bank 54,upwardly from this space 63 past thelevel of the center of the drum andforwardly and then inwardly to a space 64 above the drum and below thefront part of the economizer. The boiler casing 62 on the left-hand sideof the boiler is designed so as to lead gases flowing upwardly andoutwardly through the rows of screening tubes 58, the superheater 59,and the bank 56 to a space 65 above the bank 56, upwardly from thisspace 65 past the level of the center of the drum 50 and rearwardly andthen inwardly to a space 66 above the drum and below the rear part ofthe economizer. Insulation 67 extending around the front upperright-hand quadrant of the drum and from the top of the front part ofthe drum to a downward extension 68 of the left-hand wall 69 of the gasuptake 60 forms the bottom of the space 64, and insulation 70 extendingaround the rear upper left-hand quadrant of the drum and from the top ofthe rear part of the drum to a downward extension 71 of the right-handwall 72 of the gas uptake 60 forms the bottom of the space 66. Theinsulation 67 extends rearwardly and insulation 70 extends forwardly toa vertical plate 73 whose lower edge embraces the upper semi-circle ofthe drum and whose upper edge is horizontal a short distance above theinsulations 67 and 70.

Between the spaces 64 and 66 there is pivoted on a horizontal axis atits lower edge 80, which is transverse to the axis of the drum 50, aswinging damper 81, which has suitably secured at one end of itsoperating spindle a counter-weight 82 and at the other end thereofoperating means 83, and is adapted to be turned between a position inwhich it extends forwardly and upwardly at an angle of 45 degrees,through a neutral position in which it extends vertically upwardly, to aposition in which it extends upwardly and rearwardly at an angle of 45degrees.

The economizer 61 comprises tube lengths extending parallel to the axisof the drum 5% and arranged in horizontal rows and in fourteen verticalrows. The group 84 of the lower seven rows is spaced from the group 85of the upper seven rows. The gas flow upwardly through the lower groupof economizer tube rows is subdivided by thirteen vertical baffies 86extending transversely of the economizer tubes into fourteen gaspassages 99. Downward extensions 86 of the baffles 86 are provided ofsuch lengths that their ends lie closely adjacent the arc of swing ofthe upper edge of the damper '31; the five front bafile extensions 86'are sloped rearwardly and the five rear bafiie extensions 86' are slopedforwardly to- Wards the vertical through the axis or" the hai'fie 51.

The gas flow through the upper group of ecenomizer tube rows issubdivided by fourteen baffles extending transversely of the economizertubes into fifteen gas passages 129.

The baflles 115 are staggered with regard to the bafiies 86 and in thespace between the lower economizer tube group 84 and the uppereconomizer tube group 85 is disposed a series of thirteen pivoteddampers 345 having their axes of rotation adjacent the upper edges ofthe baffles 86, and each arranged so that its upper edge can be broughtadjacent to the lower edge of one or adjacent the lower edge of theother of those two of the baffles 115 lying closest to the verticalplane through the axis of the bafile of the lower series 86 to which thedamper is adjacent. Operating means 158 are provided for movingsimultaneously all the dampers from one of the said positions to theother;

When the damper 81 is moved from a position in which the upper edge isadjacent to one of the baffle extensions 86 to a position in which itsupper edge is adjacent another of the baffie extensions 86', the flowareas of the two gas paths, each consisting of one or more of thepassages 99, through the lower group 84 of economizer tube rows, whichgas paths are respectively in series with the gas passes through thescreening tubes 57 and vapor generating tube bank 54, and through thescreening tubes 58, superheater 59, and vapor generating tube bank 56,are differentially varied to control the degree of superheat, in themanner described in connection with the operation of the damper 13 withreference to Fig. 1. The relatively large number of the bafiies 86provides a relatively fine control of super-heat although the damper 81may not be moved to positions so that its upper edge is between two ofthe baffle extensions. The fineness of superheat control is increased bythe provision of the dampers 145 controlling the gas flows to thepassages 12? between the baffles 115 in the upper group of economizertube rows;

thus the dampers 145 can act to extend the bailles 86 eitherrespectively to the :bafiles 11-5, or, if the dampers are moved to theirother extreme positions, respectively to the bafides 115, and thus foreach possible distribution of the total gas flow through the passages99- there corresponds two possible distributions of the total gas flowto the passages 129. As shown in Fig. 4 the upper edge of the damper 81is adjacent the extension 86' of the fourth bafiie 86 and the dampers145 extend the bafiles 86 to the respective baflies 115 at the frontthereof.

The present invention thus provides a vapor generating and superheatingunit in which the superheated vapor temperature can be closely regulatedby varying the amount of the heating gases passing over the superheatingsurface, While a high overall thermal efiiciency for the unit ismaintained by the use of auxiliary heat absorbing surface and control ofthe heating gas flow over said auxiliary surface to effect a minimumunbalance of the draft loss and gas outlet temperature between a gasflow path containing the superheating surface, vapor generating surface,and a portion of the auxiliary surface and a second gas flow pathcontaining Vapor generating surface and the remaining port-ion of theauxiliary surface.

While in accordance with the provisions of the statutes I haveillustrated and described herein the best form of the invention nowknown to me, those skilled in the art will understand that changes maybe made in the form of the apparatus disclosed without departing fromthe spirit of the invention covered by my claims, and that certainfeatures of the invention may sometimes be used to advantage without acorresponding use of other features.

I claim:

1. A tubular vapor generating and superheating unit comprising acombustion chamber, a pair of parallel gas passes opening to saidcombustion chamber, a vapor superheater having its heat absorbingsurface positioned in one of said gas passes so that .the vaportemperature at the outlet from said superheater may be controlled byregulation of the distribution of the gas flow between said gas passes,a plurality of heating gas passages in series with said gas passes, anauxiliary heat exchanger in said heating gas passages, and controldamper means at the heating gas inlet side of said heating gas passagesmovable difierentially to vary the effective flow areas of said heatinggas passages respectively and thereby to regulate the distribution ofgas flow between said gas passes.

2. A tubular vapor generating and superheating unit comprising acombustion chamber, vapor generating tube banks at opposite sides ofsaid combustion chamber, a group of vapor superheating tubes arrangedadjacent one of said tube banks, a casing for said unit arranged toprovide a gas uptake and gas passes adapted to lead the heating gasesflowing from the respective tube banks to said gas uptake, an auxiliaryheat exchanger in said gas uptake, a series of bafiles arranged tosubdivide the heating gas flow over said heat exchanger into separateheating gas passages, and a swinging damper movable to selectivelydetermine Whether a heating gas passage between adjacent bafiles shallreceive gas from one or the other of the said gas passes.

3. A tubular vapor generating and superheating unit comprising acombustion chamber, oppositely inclined vapor generating tube banks atopposite sides of said combustion chamber, a central upper vapor andliquid drum and a pair of lower laterally spaced liquid drums connectedto corresponding tube banks, a group of vapor superheating tubesarranged adjacent one of said tube banks, a casing for said unitarranged to provide passages adapted to lead the heating gases flowingfrom the respective tube banks to respective spaces above the vapor andliquid drum, an economizer in a gas uptake above said spaces, a seriesof bafiies arranged to subdivide the gas flow over said economizer intoseparate gas passages, and a swinging damper movable to selectivelydetermine whether a gas passage between adjacent bafiles shall receivegas from one or the other of the said spaces.

4. A tubular vapor generating and superheating unit comprising acombustion chamber, oppositely inclined vapor generating tube banks atopposite sides of said combustion chamber, a central upper horizontallyelongated vapor and liquid drum and a pair of lower laterally spacedliquid drums connected to corresponding tube banks, said drums=havingtheir longitudinal axes substantially parallel to one another, a groupof vapor superheating tubes arranged adjacent one of said tube banks, acasing for said unit arranged to provide passages adapted to lead theheating gases flowing from the respective tube banks to respectivespaces above the front and rear parts of the vapor and liquid drum, aneconomizer in a gas uptake above said spaces, a series of bafilesextending transversely of the longitudinal axis of the vapor and liquiddrum and arranged to subdivide the gas flow over said economizer intoseparate gas passages, and a swinging damper movable to selectivelydetermine whether a gas passage between adjacent baffles shall receivegas from one or the other of the said spaces.

5. A tubular vapor generating and superheating unit comprising acombustion chamber, oppositely inclined vapor generating tube banks atopposite sides of said combustion chamber, a central upper vapor andliquid drum and a pair of lower laterally spaced liquid drums connectedto corresponding tube banks, a group of vapor superheating tubesarranged adjacent one of said tube banks, a casing for said unitarranged to provide passages adapted to lead the heating gases flowingfrom the respective tube banks to respective spaces above the vapor andliquid drum, an economizer in a gas uptake above said spaces, a seriesof bafiles arranged to subdivide the gas flow over said economizer intoseparate gas passages, and a swinging damper movable to selectivelydetermine whether a gas passage between adjacent baffles shall receivegas from one or the other of the said spaces, said baffles having theirends adjacent said damper terminating in an arc of a circle having itscenter on the axis of rotation of said swinging damper.

6. A tubular vapor generating and superheating unit comprising acombustion chamber, oppositely inclined vapor generating tube banks atopposite sides of said combustion chamber, a central upper vapor andliquid drum and a pair of lower laterally spaced liquid drums connectedto corresponding tube banks, a group of vapor superheating tubesarranged adjacent one of said tube banks, a casing for said unitarranged to provide passages adapted to lead the heating gases flowingfrom the respective tube banks to respective spaces above the vapor andliquid drum, an economizer in a gas uptake above said spaces, a seriesof baffles arranged to subdivide the gas flow over said economizer intoseparate gas passages, and a swinging damper movable to selectivelydetermine Whether a gas passage between adjacent bafiles shall receivegas from one or the other of the said spaces, said baflies having theirends adjacent said damper terminating in an arc of a circle having itscenter on the axis of rotation of said swinging damper and the bafiieends adjacent the damper remote from the plane of the neutral positionof said damper being inclined towards the damper axis.

7. A tubular vapor generating and superheating unit comprising acombustion chamber, vapor generating tube banks separately receivingheating gases from said combustion chamber, a group of vaporsuperheating tubes arranged adjacent one of said tube banks, a casingfor said unit arranged to provide a heating gas uptake and passagesadapted to lead the heating gases flowing from the respective tube banksto said gas uptake, an economizer in said gas uptake, a series ofbaffies arranged to subdivide the gas flow over said economizer intoseparate gas passages, a swinging damper movable to selectivelydetermine whether a gas passage between adjacent bafiles shall receivegas from one or the other of the said gas passes, and supplementarydamper means arranged to cooperate with said swinging damper to completethe closure of the gas pass containing said vapor superheating tubes.

8. A tubular vapor generating and superheating unit comprising acombustion chamber, oppositely inclined vapor generating tube banks atopposite sides of said combustion chamber, a central upper horizontallyelongated vapor and liquid drum and a pair of lower laterally spacedliquid drums connected to corresponding tube banks, said drums havingtheir longitudinal axes substantially parallel to one another, a groupof vapor superheating tubes arranged adjacent one of said tube banks, acasing for said unit arranged to provide passages adapted to lead theheating gases flowing from the respective tube banks to respectivespaces above the front and rear parts of the vapor and liquid drum, anauxiliary heat exchanger in a gas uptake above said spaces, a series ofbaffles extending transversely of the longitudinal axis of the vapor andliquid drum and arranged to subdivide the gas flow over said heatexchanger into separate gas passages, and a swinging damper movable toselectively determine whether a gas passage between adjacent bafliesshall receive gas from one or the other of the said spaces.

9. A tubular vapor generating and superheating unit comprising acombustion chamber, oppositely inclined vapor generating tube banks atopposite sides of said combustion chamber, a central upper horizontallyelongated vapor and liquid drum and a pair of lower laterally spacedliquid drums connected to corresponding tube banks, said drums havingtheir longitudinal axes. substantially parallel to one another, a groupof vapor superheating tubes arranged adjacent one of said tube banks, acasing for said unit arranged to provide passages adapted to lead theheating gases flowing from the respective tube banks to respectivespaces above the vapor and liquid drum, an auxiliary heat exchanger in agas uptake above said spaces having upper and lower sections, a seriesof baffles extending transversely of the longitudinal axis of the vaporand liquid drum and arranged to subdivide the gas flow over said heatexchanger lower section into separate gas passages, a swinging dampermovable to selectively determine whether a gas passage between adjacentbafiles shall receive gas from one or the other of the said spaces, asecond series of baffles extending transversely of the longitudinal axisof the vapor and liquid drum and arranged to subdivide the gas fiow oversaid heat exchanger upper section into separate gas passages, and aseries of swinging dampers positioned between said economizer upper andlower sections and movable to act as extensions of the first series ofbattles either to one or another set of said second series of bafiies.

ll). A tubular vapor generating and superheating unit comprising acombustion chamber, oppositely inclined vapor generating tube banks atopposite sides of said combustion chamber, a central upper horizontallyelongated vapor and liquid drum and a pair of lower laterally spacedliquid drums connected to corresponding tube banks, said drums havingtheir longitudinal axes substantially parallel to one another, a groupof vapor superheating tubes arranged adjacent one of said tube banks, acasing for said unit arranged to provide passages adapted to lead theheating gases flowing from the respective tube banks to respectivespaces above the front and rear parts of the vapor and liquid drum, aneconomizer in a gas uptake above said spaces having upper and lowersections, a series of bafies extending transversely of the longitudinalaxis of the vapor and liquid drum and arranged to subdivide the gas'fiow over said economizer lower section into separate gas passages, aswinging damper movable to selectively determine whether a gas passagebetween adjacent baflies shall receive gas from one or the other of thesaid spaces, a second series of bafiles extending transversely of thelongitudinal axis of the vapor and liquid drum and arranged to subdividethe gas flow over said economizer upper section into separate gaspassages, said second series of bafiies being staggered relative to thefirst series of bafiies, a series of swinging dampers positioned betweensaid economizer upper and lower sections and movable to act asextensions of the first series of baffles either to one or another setof said second series of baffles, and means for simultaneously operatingsaid series of swinging dampers.

References Cited in the file of this patent UNITED STATES PATENTSRe.21,257 Lucke Nov. 7, 1939 3 1,502,858 Little July 29, 1924 2,048,039.Stillman July 21, 1936 2,217,512 Donley Oct. 8, 1940 2,415,123 ZollerFeb 4, 1947 2,553,493 Woolley May 15, 1951 FOREIGN PATENTS 316,058 GreatBritain July 25, 1929

